1. Field of the Invention
The present invention relates to a step motor, and particularly, to a step motor in which a pressing structure of a thrust bearing supporting an axial end of a lead screw is improved.
2. Discussion of the Related Art
Generally, a step motor is widely used in various fields such as an optical apparatus, a printer and an automatically controlled machine tool. In the step motor, a transfer member is engaged with a lead screw so as to be transferred in an axial direction by driving of the motor.
The step motor typically includes a rotor including a lead screw, a stator having a cylindrical shape in which the rotor is received in the stator, a housing which receives the rotor and the stator, a thrust bearing which presses an end of the lead screw, a coil spring which presses the thrust bearing, and a cap which inhibits deviation of the coil spring.
In the conventional step motor, the rotor is disposed inside the stator, the stator is received in the housing, the thrust bearing is disposed in the housing, the coil spring is assembled at the thrust bearing, and then the cap is fixed to the housing.
However, the conventional step motor has some problems in that it is difficult to fix the cap to the housing after the coil spring is disposed at the thrust bearing, and also it is not facile to perform assembling operations due to the deviation of the coil spring and the like.